Signal amplification using a reference plane with alternating impedance

ABSTRACT

An electronic structure includes a conductor layer; an insulation layer adjacent to the conductor layer; an Alternating Impedance Electromagnetic Bandgap (AI-EBG) layer adjacent to the conductor layer; and a signal driver, a transmission line, and a destination device overlaid on the AI-EBG layer, such that the AI-EBG layer induces an alternating change to an impedance in the transmission line. The alternating change to the impedance creates a reflection signal to an initial signal on the transmission line, and the reflection signal and the initial signal combine to create an amplified signal.

BACKGROUND

The present disclosure relates to the field of electronic circuits, andspecifically to electronic circuits that carry signals. Still moreparticularly, the present disclosure relates to amplifying signals usingpassive amplifiers.

SUMMARY

In an embodiment of the present invention, an electronic structureincludes a conductor layer; an insulation layer adjacent to theconductor layer; an Alternating Impedance Electromagnetic Bandgap(AI-EBG) layer adjacent to the conductor layer; and a signal driver, atransmission line, and a destination device overlaid on the AI-EBGlayer. The AI-EBG layer induces an alternating change to an impedance inthe transmission line. The alternating change to the impedance creates areflection signal to an initial signal on the transmission line, and thereflection signal and the initial signal combine to create an amplifiedsignal.

In an embodiment of the present invention, a device includes anelectronic structure. The electronic structure includes: a conductorlayer; an insulation layer adjacent to the conductor layer; anAlternating Impedance Electromagnetic Bandgap (AI-EBG) layer adjacent tothe conductor layer; and a signal driver, a transmission line, and adestination device overlaid on the AI-EBG layer. The AI-EBG layerinduces an alternating change to an impedance in the transmission line.The alternating change to the impedance creates a reflection signal toan initial signal on the transmission line, and the reflection signaland the initial signal combine to create an amplified signal.

In an embodiment of the present invention, a method amplifies a signalon a transmission line. A driver transmits an initial signal on atransmission line, which is overlaid on an AlternatingImpedance-Electromagnetic BandGap (AI-EBG) structure (i.e., a referenceplane) on a circuit board. The AI-EBG structure induces an alternatingchange to an impedance in the transmission line. The alternating changeto the impedance creates a reflection signal to an initial signal on thetransmission line, and the reflection signal and the initial signalcombine to create an amplified signal.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts an exemplary AI-EBG structure used in accordance with oneor more embodiments of the present invention;

FIG. 2 illustrates various impedances in components of AI-EBG unit cellsin an AI-EBG layer;

FIG. 3 depicts a transmission line that is overlaid on top of the AI-EBGstructure;

FIG. 4 illustrates a signal amplification induced by the AI-EBGstructure according to measured test results by the present inventor;and

FIG. 5 is a high level flow chart of one or more steps performed by oneor more hardware devices to amplify a signal using an AI-EBG structure.

DETAILED DESCRIPTION

In high-speed digital systems or mixed-signal systems, signalamplification is required for signals being transmitted alongtransmission lines since transmitted signals attenuate (decay). Thissignal attenuation is caused by dielectric loss in dielectric materialsused in the transmission lines and/or by metal loss related to metalsurface roughness of the transmission lines and/or surroundingmaterials.

In the prior art, powered active amplifiers such as transistors havebeen employed to amplify signals being transmitted along thetransmission lines in such systems. However, powered active amplifierspose several problems.

First, the complexity of systems (i.e., circuits) that use activeamplifiers is increased by the presence of the active amplifiers. Thisleads to additional cost in manufacturing the circuits.

Second, active amplifiers generate heat, thus requiring additionalcooling mechanisms (e.g., fans, heat sinks, etc.) for thesystem/circuitry, which further increases the complexity and cost of thecircuit.

Third, active amplifiers generate their own electronic “noise” (unwantedelectronic interference), which induces signal pollution on othertransmission lines.

In order to address the problems associated with the use of activeamplifiers in amplifying signals on transmission lines in circuits, thepresent invention presents a novel, elegant, cost-effective, and usefuldesign that uses passive elements to amplify signals being transmittedon transmission lines within a circuit. Specifically, the presentinvention utilizes Alternating Impedance-Electromagnetic Bandgap(AI-EBG) structures to induce signal amplification by creating additivereflective signals in a transmission line.

With reference now to FIG. 1, an exemplary AI-EBG structure 101 asutilized in one or more embodiments of the present invention ispresented. As shown in FIG. 1, the AI-EBG structure 101 includes threemain components: an AI-EBG layer 103, an insulation layer 109, and aconductor layer 111.

AI-EBG layer 103 (i.e., a reflective plane) includes an AI-EBG unit cellarray 113, which is made up of multiple AI-EBG unit cells, such as theAI-EBG unit cell 105 shown in the first expanded view. As depicted infurther detail in FIG. 1, each AI-EBG unit cell 105 includes a metalpatch 107 and one or more metal branches, depicted in FIG. 1 as metalbranches 1-4. As discussed below, metal branches 1-4 in combination withmetal patch 107 induce changes to impedances on nearby transmissionlines.

Below the AI-EBG layer 103 is insulation layer 109, which in anembodiment is made of FR-4, which is a glass-reinforced epoxy laminatematerial. That is, FR-4, which is fire resistant (FR) and complies withUnderwriters Laboratories standard UL94v-0 (4), is a composite materialcomposed of woven fiberglass cloth that is embedded with an epoxy resin.While FR-4 is an example of insulation material that can be used ininsulation layer 109, other dielectric materials may be utilized ininsulation layer 109 based on application/design factors.

Below insulation layer 109 is conductor layer 111, which is made ofcopper or other conducting material, and which supplies voltage to theAI-EBG structure 101 and/or other devices as described herein.

The impedances Z in the metal branches 1-4 shown in FIG. 1(Z_(1(branch))-Z_(4(branch))) differ from the impedance Z in the metalpatch 107 (Z_((patch))). These differences in impedances Z are theresult of metal patch 107 being thicker than metal branches 1-4. Forexample, the metal branches 1-2 are thinner than metal patch 107 in theAI-EBG unit cell 105 shown in FIG. 2. These different impedances Z causeinduced changes to impedances Z on nearby transmission lines, as nowdescribed.

With reference now to FIG. 3, a circuit board 301 that embodies one ormore of the inventive elements of the present invention is presented.Circuit board 301 includes an AI-EBG layer 303 (analogous to AI-EBGlayer 103 shown in FIG. 1), an insulation layer 309 (analogous toinsulation layer 109 shown in FIG. 1), and a conductor layer 311(analogous to conductor layer 111 shown in FIG. 1).

As shown in FIG. 3, AI-EBG layer 303 is connected to ground (GND), andincludes an AI-EBG unit cell array 313 (analogous to AI-EBG unit cellarray 113 shown in FIG. 1).

A signal driver 315 (e.g., from a digital circuit such as a fieldprogrammable gate array—FPGA, etc.) is powered by the voltage (VDD) inconductor layer 311 by a connection supplied by a conducting via, suchas the depicted via 321. Via 321 provides an electrical connection fromthe voltage VDD to the signal driver 315, but is electrically insulatedfrom AI-EBG layer 303 and insulation layer 309.

Signal driver 315 generates and places a signal on transmission line317, which carries the signal to a terminator 319 (e.g., a receivingsub-circuit, input/output port, etc.), which is coupled to ground by aresistor 321.

The voltage VDD from conductor layer 311 inherently induces a baseinduced voltage onto AI-EBG layer 303. Due to the different impedancesin the metal patches and metal branches described above, varyingimpedances Z are induced onto transmission line 317, resulting in avoltage bump to the signal being transmitted on the transmission line317.

To investigate the voltage bump just described, time domainreflectometry (TDR) measurements are taken to measure the characteristicimpedance of the transmission line. In a TDR measurement, an injectedvoltage pulse (e.g., from signal driver 315) propagates down the signalline (e.g., transmission line 317), reflects off the discontinuity(i.e., the change to impedance in the signal line induced by the AI-EBGlayer 303), and then returns to form a pulse on the oscilloscope. Eachchange in characteristic impedance causes the TDR trace to bump up ordown to a new impedance level. Increasing impedance implies increasedinductance, reduced capacitance, or both, which are induced by theAI-EBG layer 303. Conversely, decreasing impedance implies increasedcapacitance, reduced inductance, or both, which are induced by theAI-EBG layer 303. These changes in impedance lead to changes in signalvoltages, such that the signal amplitude at the far end of thetransmission line is bigger than that at the output of the FPGA(driver).

Continue now to assume that a signal propagates from the FPGA to theterminator at the end of transmission line. When a signal passes above ametal branch (in one or more of the AI-EBG unit cells 105 in an AI-EBGunit cell array 113), the TDR trace bumps up. That is, as the signal ontransmission line 317 moves above one of the AI-EBG units in AI-EBG unitarray 313 in FIG. 3, the initial impedance Z₁ of the transmission line317 changes to impedance Z₂. The reflection coefficient formula for thiscase is given as:

$\Gamma = {\frac{v_{n}^{-}}{v_{n}^{+}} = \frac{Z_{o,{n + 1}} - Z_{o,n}}{Z_{o,{n + 1}} + Z_{o,n}}}$

where Γ is a reflection coefficient, V_(n) ⁺ is a voltage traveling inpositive direction at nth transmission line, v_(n) ⁻ is a voltagetraveling in negative direction at nth transmission line, Z_(o,n) is acharacteristic impedance at nth transmission line, and Z_(o,n+1) is acharacteristic impedance at (n+1)th transmission line.

Since Z₂>Z₁ in this case, the reflected wave is a positive copy of theincident wave. The incident and reflected waves superimpose. The voltageis continuous at the discontinuity, so the signal continues onto thesecond transmission line with peak amplitude based on the total voltageon the first line. When the incident and reflected waves have the samesign, they add, and the voltage signal on the second transmission islarger. This situation continues when an injected signal passes over ametal branch in a gap. This is because periodic gaps in AI-EBG structuremake discontinuities in impedance profile and these discontinuities makereflection coefficient positive.

As shown in graph 400 in FIG. 4, the voltage of the signal as it leftthe signal driver 315 in FIG. 3 is depicted as line 402. However, thevoltage of the signal as it arrived at terminator 319 is depicted asline 404. The voltage “bump” is the result of a combination of initialsignals and reflected signals caused by changes to impedance in thetransmission line 317. Note that this voltage amplification/bump isentirely passive, and does not require any additional drivers,amplifiers, etc.

Note that the electronic structure depicted in FIGS. 1-3 may be acomponent of a larger device, such as a vehicle (e.g., automobile,truck, aircraft, watercraft, etc.), an appliance (e.g., a refrigerator,a washing machine, etc.), manufacturing equipment (e.g., a computernumerical control—CNC machine), etc.

With reference now to FIG. 5, a high level flow chart of one or moresteps performed by one or more hardware devices in an AI-EBG structureto amplify a signal traveling on a transmission line is presented.

After initiator block 501, a driver (e.g., signal driver 315 shown inFIG. 3) transmits an initial signal on a transmission line (e.g.,transmission line 317 in FIG. 3), as described in block 503. As depictedin FIG. 3, the transmission line is overlaid on an AlternatingImpedance-Electromagnetic BandGap (AI-EBG) structure on a circuit board.That is, the AI-EBG structure 301 shown in FIG. 3 is part of a circuitboard. Overlaid on top of the AI-EBG structure 301 are one or moretransmission lines, such as transmission line 317 shown in FIG. 3.

As described in block 505 in FIG. 5, the AI-EBG structure induces analternating change to an impedance in the transmission line. Thealternating change to the impedance creates a reflection signal to aninitial signal on the transmission line. The reflection signal and theinitial signal combine to create an amplified signal, as describedherein.

The flow chart ends at terminator block 507.

Any methods described in the present disclosure may be implementedthrough the use of a VHDL (VHSIC Hardware Description Language) programand a VHDL chip. VHDL is an exemplary design-entry language for FieldProgrammable Gate Arrays (FPGAs), Application Specific IntegratedCircuits (ASICs), and other similar electronic devices. Thus, anysoftware-implemented method described herein may be emulated by ahardware-based VHDL program, which is then applied to a VHDL chip, suchas a FPGA.

Having thus described embodiments of the present invention of thepresent application in detail and by reference to illustrativeembodiments thereof, it will be apparent that modifications andvariations are possible without departing from the scope of the presentinvention defined in the appended claims.

1. An electronic structure comprising: a conductor layer; an insulationlayer adjacent to the conductor layer; an Alternating ImpedanceElectromagnetic Bandgap (AI-EBG) layer adjacent to the conductor layer;and a signal driver, a transmission line, and a destination deviceoverlaid on the AI-EBG layer, wherein the AI-EBG layer induces analternating change to an impedance in the transmission line, wherein thealternating change to the impedance creates a reflection signal to aninitial signal on the transmission line, and wherein the reflectionsignal and the initial signal combine to create an amplified signal. 2.The electronic structure of claim 1, wherein the AI-EBG layer comprises:an AI-EBG unit cell array of AI-EBG unit cells, wherein each AI-EBG unitcell comprises a metal patch having a first thickness and one or moremetal branches having a second thickness, wherein the one or more metalbranches extend away from the metal patch, and wherein the firstthickness of the metal patch is greater than the second thickness of theone or more metal branches.
 3. The electronic structure of claim 1,further comprising: a ground connected to the AI-EBG layer, wherein theterminator is connected to the AI-EBG layer and the ground.
 4. Theelectronic structure of claim 1, further comprising: a power sourceconnected to the conductor layer; and a conducting via through theAI-EBG layer and the insulation layer that electrically couples thepower source to the signal driver, wherein the conducting viaelectrically insulates the AI-EBG layer and the insulation layer fromthe power source.
 5. A device comprising an electronic structure,wherein the electronic structure comprises: a conductor layer; aninsulation layer adjacent to the conductor layer; an AlternatingImpedance Electromagnetic Bandgap (AI-EBG) layer adjacent to theconductor layer; and a signal driver, a transmission line, and adestination device overlaid on the AI-EBG layer, wherein the AI-EBGlayer induces an alternating change to an impedance in the transmissionline, wherein the alternating change to the impedance creates areflection signal to an initial signal on the transmission line, andwherein the reflection signal and the initial signal combine to createan amplified signal.
 6. The device of claim 5, wherein the AI-EBG layercomprises: an AI-EBG unit cell array of AI-EBG unit cells, wherein eachAI-EBG unit cell comprises a metal patch having a first thickness andone or more metal branches having a second thickness, wherein the one ormore metal branches extend away from the metal patch, and wherein thefirst thickness of the metal patch is greater than the second thicknessof the one or more metal branches.
 7. The device of claim 5, furthercomprising: a ground connected to the AI-EBG layer, wherein theterminator is connected to the AI-EBG layer and the ground.
 8. Thedevice of claim 5, further comprising: a power source connected to theconductor layer; and a conducting via through the AI-EBG layer and theinsulation layer that electrically couples the power source to thesignal driver, wherein the conducting via electrically insulates theAI-EBG layer and the insulation layer from the power source. 9.(canceled)